An air filter of an internal combustion engine of a motor vehicle known in the market has a filter housing in which a flat filter element is arranged. The filter housing comprises a filter cup and a filter cover that can be separated from the filter cup. The flat filter element comprises a filter medium which is folded in a zigzag shape to a filter bellows. The filter bellows has approximately the shape of a parallelepiped. In flat filter elements, the filter media are not closed, i.e., end face folds, like end face edges, are not connected to each other. In contrast thereto, in round filter elements the filter media are closed, i.e., their end face folds are connected to each other. The end face folds are the two outermost folds on opposite end faces of the filter bellows. End face rims are the two free rims of the filter medium which extend along the end face folds and delimit them at the end faces of the filter bellows. The end face edges of the filter bellows are the two other free rims of the filter bellows which extend between the end face rims and extend in accordance with the folding of the filter bellows. The fold edges are those edges along which the filter medium is folded. In the zigzag-shaped folded parallelepipedal filter bellows, the end face rims and the fold edges are straight and extend parallel to each other. The end face edges extend in a zigzag shape and perpendicular to the end face rims and the fold edges. On a sealing rim of the filter bellows that surrounds the inflow side, a seal of polyurethane (PUR) is arranged. The seal surrounds, circumferentially closed, the inflow side relative to an imaginary central axis of the sealing rim. The seal projects past the filter bellows relative to the central axis in radial direction outwardly. The flat filter element is axially inserted relative to the central axis into the filter cup. The filter cup has a sealing surface which relative to the central axis extends in radial direction outwardly and on which a side of the seal of the flat filter element in axial direction is resting seal-tightly. The filter cover has also a sealing surface which relative to the central axis extends in radial direction outwardly. When the filter cover is mounted, its sealing surface in axial direction is resting seal-tightly on the side of the seal that is positioned opposite the sealing surface of the filter cup. The seal of the flat filter element is then tightly clamped between the sealing surfaces of the filter cover and the sealing surface of the filter cup. In this way, the seal seals the inflow-side raw side of the flat filter element from the outflow-side clean side. Thus, on the filter head and on the filter cover a sealing surface is required, respectively. The two sealing surfaces must be arranged such that they can interact with each other for compressing the seal.
The object of the invention is to configure a flat filter element, a filter, and a support device of the aforementioned kind with which the expenditure for realizing a sealing action of the raw side relative to the clean side can be reduced. In particular, the expenditure with regard to required sealing surfaces is to be reduced. Moreover, penetration of leak air is to be prevented.